Former Swiss banker Rudolf Elmer, who worked for eight years in the Cayman Islands, a renowned offshore tax haven in the Caribbean, personally gave Assange two CDs of data at a London press conference.

Elmer said he wanted the world to know the truth about money concealed in offshore accounts and the systems in place to keep it secret.

He handed over the data at the Frontline Club — WikiLeaks\’ British HQ — as Assange put in a rare appearance away from the remote country house of the club\’s founder, where he has been bailed to live while he awaits extradition proceedings.

"I am here today to support him," Assange told reporters.

"He is a whistleblower and he has important things to say."

The Australian promised "full revelation" of the data but said it would be weeks before any of the information could be checked and published by the WikiLeaks website.

Profile: Rudolf Elmer

Elmer declined to give the names of those on the CDs or say how many individuals were involved, though he mentioned the 2,000 figure in British newspaper The Observer, which published an interview with him Sunday.

He has said the information includes details on around 40 politicians, multinational companies and financial institutions from the United States, Europe and Asia all secretly avoiding paying tax.

"The only hope I have is to get society to know what\’s going on," he said.

"I have been there, I have done the job, I know what the day-to-day business is, I know how much is documented there and how much is not.

"I am against the system. I know how the system works. I want to let society know how this system works because it\’s damaging our society.

"We\’re going to talk about the system and that\’s why I\’m here.

"The money is hiding in offshore banking secret jurisdictions."

He said he was offered money for his silence and that he offered the information to former German finance minister Peer Steinbrueck for free but had received no response.

Assange said WikiLeaks has so far released 2.3 percent of the 250,000 US diplomatic cables and was struggling with the volume of data.

The Australian is on bail in Britain awaiting Sweden\’s attempt to extradite him for questioning on sexual assault allegations.

A full extradition hearing will be heard at a London court on February 7-8.

Elmer was dismissed in 2002 after eight years as the chief operating officer of Julius Baer Bank in the Cayman Islands.

He is to appear before a Zurich court on Wednesday to answer to charges of bank secrecy violations, after he passed on clients\’ data to WikiLeaks in 2007.

The move led to tax evasion prosecutions in several countries against these clients.

In 2008 a former employee of Liechtenstein\’s biggest bank sold data on client accounts in the secretive Alpine banking haven to the German secret service for five million euros.

And last year officials in the German state of North Rhine-Westphalia bought a computer disc for a reported 2.5 million euros with information on secret Swiss accounts.

As a result German tax authorities recovered 1.6 billion euros in 2010 from holders of the accounts, according to the weekly Der Spiegel.